In the field of testing digital electronic circuits, the HP/Agilent Technology Model D20 Digital Functional Test System has been used for some time, and is described more fully in a Product Note dated Aug. 1, 1991.
As to U.S. patents, U.S. Pat. No. 4,692,886 (Miki et al.) describes a digital pattern generator that generates various kinds of digital pattern signals. The generator includes a first memory that stores an execution signal, an area control signal and a digital pattern, a program counter that generates a first address signal in accordance with the execution signal read from the first memory and a first clock signal, and the first memory is addressed by the first address signal. A second memory includes a plurality of memory areas each storing a digital pattern, and a capacity of each the memory area corresponds to that of the first memory. When the memory area of the second memory is selected by the area control signal read from the first memory and the selected memory area is addressed by the first address signal, the second memory acts as an auxiliary memory of the first memory.
U.S. Pat. No. 5,905,967 (Botham) describes automatic test equipment with programmable timing generators that generate digital signals and analog signals. The digital timing generator can be programmed to generate timing signals with a resolution finer than that of the master clock of the timing generator. Extremely fine resolution is achieved by specifying the numerator and denominator of a fractional portion of a period. A similar arrangement is used to allow fine frequency resolution for the analog timing generator. The fine resolution achievable with the timing generators allows the digital timing generator to be synchronized to the analog timing generator.
In view of the relatively long time since the original application of the HP/Agilent D20 in or about 1991, it would be desirable to provide a replacement for this digital functional test system that is current vis-à-vis technological advances since 1991.